Probe the Electron Spin Polarization of the Otherwise Unobservable 3MLCT Triplet State Through Polarization Transfer Accompanying the Intramolecular Triplet-Triplet Energy Transfer in Pt(II)-Salen Schiff Base Complexes
Year: 2026
Authors: Wu Y.R., Sukhanov A.A., Iagatti A., Zhao J.Z., Voronkova V.K., Dick B., Gurzadyan G.G., Di Donato M.
Autors Affiliation: Dalian Univ Technol, Sch Chem Engn, State Key Lab Fine Chem, Dalian, Peoples R China; Russian Acad Sci, Zavoisky Phys Tech Inst, FRC Kazan Sci Ctr, Kazan, Russia; LENS European Lab Nonlinear Spect, Florence, Italy; Natl Inst Opt Natl Res Council, INO CNR, Sesto Fiorentino, Italy; Univ Regensburg, Inst Phys & Theoret Chem, Lehrstuhl Phys Chem, Regensburg, Germany; Dalian Univ Technol, Inst Artificial Photosynth, Sch Chem Engn, State Key Lab Fine Chem, Dalian, Peoples R China; Natl Acad Sci Armenia, A B Nalbandyan Inst Chem Phys, Yerevan, Armenia; ICCOM CNR, Florence, Italy.
Abstract: The non-Boltzmann population of the triplet sublevels in Pt(II)-Schiff base complexes, and other phosphorescent transition metal complexes, exhibits large zero-field splitting (ZFS, similar to 25 cm-1), preventing a time-resolved electron paramagnetic resonance (TREPR) study. To investigate the intersystem crossing (ISC) electron spin selectivity of the Pt(II) complexes, we attached a perylene unit as a triplet energy acceptor. Our method relies on the conservation of spin angular momentum during the ultrafast intramolecular triplet-triplet energy transfer (TTET) from the metal-to-ligand charge transfer (3MLCT) state to the 3Pery state of the appended perylene unit, which has a small ZFS (0.05 cm-1) and can be studied with an X-band TREPR spectrometer. TTET occurs within similar to 1 ps. TREPR spectra detected no signal from the native complex, while the modified complex showed the 3Pery state spectrum with an electron spin polarization (ESP) pattern (e, a, e, a, e, a), distinct from the spin-orbit coupling (SOC)-generated 3Pery state (e, e, e, a, a, a). Based on the orientation of the two units, the population ratios of the 3MLCT sublevels were deduced as P x:P y:P z = 0.58:0.22:0.20 (in acceptor’s coordinates). Our approach offers a novel way to deduce the ISC spin selectivity in phosphorescent transition metal complexes.
Journal/Review: ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
More Information: J. Z. thanks the NSFC (W2521100, U25A20619, 22473021, and U2001222), the Research and Innovation Team Project of Dalian University of Technology (DUT2022TB10), the Fundamental Research Funds for the Central Universities (DUT22LAB610), and the State Key Laboratory of Fine Chemicals for financial support. A.A.S. and V.K.V. acknowledge financial support from the government assignment for FRC Kazan Scientific Center of RAS.KeyWords: electron paramagnetic resonance; electron spin polarization transfer; intersystem crossing; triplet state; zero-field splittingDOI: 10.1002/anie.5596109
